25(OH)D Levels in Relation to Gender, Overweight, Insulin Resistance, and Inflammation in a Cross-Sectional Cohort of Northern Italian Workers: Evidence in Support of Preventive Health Care Programs

Objective: In recent years, the welfare of workers and the prevention of chronic disabling diseases has become a topic of great interest. This study investigates serum levels of total 25-hydroxyvitamin D (25(OH)D) in a cohort of overweight-obese and insulin-resistant northern Italian indoor workers in apparent good health followed a nutritional education program.Methods: An observational cross-sectional study on 385 patients (females = 291, males = 94), age range 18-69years and body mass index (BMI) > 25kg/m(2), was performed at the Department of Occupational Medicine Milan, Italy, latitude 45.465454N. We evaluated nutritional intakes, occupational and leisure physical activity, anthropometric measurements, impedance evaluation, blood pressure, the presence of metabolic syndrome (MetS) and nonalcoholic fatty liver diseases (NAFLD) by fatty liver index (FLI). Hematologic and biochemical parameters and (25(OH)D) levels were evaluated from fasting blood samples.Results: Only 10.91% of subjects had optimal values of 25(OH)D; 17.40% of the remaining 89.09% subjects were severely deficient, with no gender difference and insufficient intake of vitamin D. Only 28% declared leisure physical activity; 39.48% had metabolic syndrome and 62.60% had an FLI > 30. An inverse relationship between 25(OH)D levels and BMI was found, with a significant reduction of total 25(OH)D serum concentrations in winter. The homeostasis model assessment-insulin resistance (HOMA-IR) is positively related to BMI and inversely related to 25(OH)D concentrations. A positive correlation between vitamin D and leisure physical activity was found. At univariate analysis adjusted for age, gender and BMI, an inverse relationship between vitamin D and FLI was observed in both genders. The correlation between 25(OH)D levels, inflammation markers, BMI, and FLI showed an increased risk of cardiovascular disease in this cohort of workers.Conclusion: Our results suggest the rationale for a large-scale screening program for vitamin D by means of easily implementable low-cost preventive supplementation.